Variable breadth impeller that provides a specific shutoff head

In a variable capacity centrifugal pump, a variable breadth impeller unit that provides a specific shutoff head comprising:

• an impeller element adapted to be rotationally mounted within the variable capacity centrifugal pump, said impeller element having a plurality of radially extending impeller vanes projecting axially therefrom and defining flow passages therebetween, at least one axial inlet in flow communication with said flow passages, at least one radial outlet in flow communication with said flow passages whereby flow is channeled under the effects of said rotating impeller element from said axial inlet through said flow passages to said radial outlet;
• a substantially solid annular movable shroud adapted to be rotationally mounted coaxially with said impeller element;
• said movable shroud including first and second surfaces disposed axially from one another in a plane substantially orthogonal to the axis of rotation of said impeller element, said first surface having a plurality of grooves formed therein for receiving said vanes of said impeller element in a meshing relationship;
• said movable shroud adapted for continuous axial movement between a fully open position defining a constant pressure maximum flow rate operating condition and a fully closed position defining a constant pressure minimum flow rate operating condition whereby the volume of said flow passages is varied;
• and
• said movable shroud further including a third surface orthogonally disposed between said first and second surfaces and defining an outer radial perimeter of said movable shroud, said third surface having a plurality of recessed grooves formed therein, said recessed grooves extending axially over a portion of said third surface between said first and second surfaces wherein said recessed grooves act as a supplemental pumping means for energizing the flow within the variable capacity centrifugal pump during operation between the constant pressure minimum flow rate condition and the shutoff condition of the variable capacity centrifugal pump whereby said specific shutoff head is achieved.

A method for adapting a variable capacity centrifugal pump to produce a specific predetermined shutoff head comprising the steps of:

• rotatably mounting an impeller element within said variable capacity centrifugal pump, said impeller element having a plurality of radially extending impeller vanes projecting axially therefrom and defining flow passages therebetween, at least one axial inlet in flow communication with said flow passages, at least one radial outlet in flow communication with said flow passages wherein a fluid is channeled under the effects of said rotating impeller element from said axial inlet through said flow passages to said radial outlet;
• rotatably mounting an annular movable shroud in coaxial alignment with said impeller element, said movable shroud having at least three surfaces including first and second surfaces disposed axially from one another in a plane substantially orthogonal to the axis of rotation of said impeller element and a third surface orthogonally disposed between said first and second surfaces and defining an outer radial perimeter of said movable shroud;
• providing said first surface of said movable shroud with a plurality of grooves formed for receiving said vanes of said impeller element in a meshing relationship;
• adapting said movable shroud for continuous axial movement between a fully open position defining a constant pressure maximum flow rate operating condition and a fully closed position defining a constant pressure minimum flow rate operating condition whereby the volume of said flow passages is varied;
• and
• providing said third surface of said movable shroud with a plurality of recessed grooves extending axially over a portion of said third surface between said first and second surfaces wherein said recessed grooves act as a supplemental pumping means for energizing the fluid within the variable capacity centrifugal pump during operation between the constant pressure minimum flow rate condition and the shutoff condition of the variable capacity centrifugal pump whereby below a specific flow rate a constantly rising head-capacity curve and said specific shutoff head are achieved.